The elusive nature of the nondual
Typically, humans flit between dual and nondual forms of consciousness without ever knowing or detecting the difference. In this brief introduction, the critical thing to bear in mind is that we all have access to dual and nondual consciousness; both are integral to the human experience. However, it is highly problematic to recognise and then cultivate a nondual view without training and direction. It is not possible to provide a comprehensive explanation of dual or nondual consciousness here and now. So I will attempt to use some simplified approximations to begin the conversation
In a typical western materialistic society such as mine, most people spend most of their time in dualistic consciousness. We could characterise the dualistic state in many ways; as a starting point, let us regard it as the point of view where one believes, as truth, the conscious and subconscious impulses generated by a brain. So while we can all find examples of irrational thoughts that we recognise as meaningless, our identity is made up of fabricated constructs that have no reality other than that which we attribute to them. So, for example, to think that others are responsible for your mental states is usually an expression of dualism, as is the belief that our wishes and goals are somehow different or more important than the wishes and goals of others.
By contrast, a nondual view enables us to distinguish between reliable mental phenomena and transient unreliable thoughts and feelings. Thus we can achieve some relative freedom in how to think, speak and act. It is this freedom that is often associated with the happiness and stability observed in nondual practitioners. So from a nondual perspective, we make the presumption that the thoughts and feelings of others may be just as important and meaningful as ours. I will stop the definitions here for now and briefly discuss what these concepts mean for meditation practice.
In traditional meditation, people begin at the beginning; if they have a reliable teacher and methods and are diligent, they can make progress. But until a practitioner realises which of the mental phenomena arising in their consciousness is transient and meaningless, then all meditation can be seen as relative. That means your practice is relative to your mental state and a range of other causes and conditions. A practitioner who has some modest experience of the nondual should be able to transcend belief in mundane phenomena knowing of their relative unimportance. That is not to say that a nondual practitioner may have arrived at a transcendent mental state; it is simply that they know the limitations of their own worldview. That, in a nutshell, is an elementary exploration of why the nondual view is essential to progress in meditation practice. Without it understanding, the inner world of our consciousness remains uncertain. While much Buddhist meditation is not explicitly nondual, it all, by its very nature, increases the ability of the student to understand nonduality.